Hydrogel derived catalyst of zinc titanate and alumina promoted with cobalt and molybdenum for hydrodesulfurization or hydrodenitrogenation

ABSTRACT

The catalytic hydrodesulfurization and/or hydrodenitrogenation of an organic sulfur compound and/or an organic nitrogen compound is carried out in the presence of a hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum.

This application is a division of application Ser. No. 644,883, filedAug. 27, 1984, now U.S. Pat. No. 4,522,709.

This invention relates to an improved catalytic process for thehydrosulfurization (HDS) of organic sulfur compounds and/or thehydrodenitrogenation (HDN) of organic nitrogen compounds.

Hydrodesulfurization is a process intended primarily to convert thesulfur in organic sulfur compounds to hydrogen sulfide.Hydrodenitrogenation is a process intended primarily to convert thenitrogen in organic nitrogen compounds to ammonia. Hydrodesulfurizationand hydrodenitrogenation will generally occur at the same time undersimilar process conditions if both organic sulfur compounds and organicnitrogen compounds are present in the feed stream. The hydrogen sulfideand/or ammonia can be removed from the feed stream after thehydrodesulfurization and/or hydrodenitrogenation process.Hydrodesulfurization and hydrodenitrogenation are processes which aretypically utilized to remove sulfur and nitrogen from ahydrocarbon-containing feedstock which also contains organic sulfurcompounds and/or organic nitrogen compounds to produce fuels which, whenburned, will meet environmental standards. The processes may be appliedto feed streams other than hydrocarbon-containing feeds if organicsulfur compounds and/or organic nitrogen compounds are present and theremoval of sulfur and/or nitrogen is desired.

The earliest hydrosulfurization and/or hydrodenitrogenation catalystswere bauxite and Fuller's earth. Later, catalysts containing cobaltmolybdate on alumina and nickel tungstate on alumina substantiallyreplaced the earlier catalyst and these catalysts are still used veryextensively.

U.S. Pat. No. 4,287,050 discloses that a catalyst composition comprisingcatalytic grade alumina, zinc titanate, cobalt and molybdenum iseffective as a hydrodesulfurization and/or hydrodenitrogenationcatalyst. However, while the catalyst disclosed by U.S. Pat. No.4,287,050 is an excellent catalyst, it is always desirable to improvethe activity of a catalyst. It is thus an object of this invention toprovide an improved catalytic process for the hydrodesulfurization oforganic sulfur compounds and/or the hydrodenitrogenation of organicnitrogen compounds using the components of the catalyst of U.S. Pat. No.4,287,050.

In accordance with the present invention, a hydrogel derived catalystcomprising zinc titanate and alumina promoted with cobalt and molybdenumis utilized as a catalyst in a hydrodesulfurization and/orhydrodenitrogenation process. The hydrodesulfurization and/orhydrodenitrogenation process is carried out under suitable conditions.The promoted hydrogel derived catalyst exhibits a substantially improvedactivity with respect to the promoted zinc titanate catalyst of U.S.Pat. No. 4,287,050.

The hydrodesulfurization and/or hydrodenitrogenation process ispreferably carried out in cycles consisting of a reaction period and aregeneration period for the catalyst. The reaction period comprisescontacting a feedstock which contains organic sulfur compounds and/ororganic nitrogen compounds with the catalyst to thereby convert thesulfur in organic sulfur compounds in the feedstock to hydrogen sulfideand also convert the nitrogen in organic nitrogen compounds to ammonia.After the reaction period, an oxygen-containing gas is passed in contactwith the catalyst to regenerate the catalyst by burning off carbonaceousmaterials which may have formed on the catalyst.

Other objects and advantages of the invention will be apparent from theforegoing brief description of the invention and the appended claims, aswell as the detailed description of the invention which follows.

Any suitable organic sulfur compound may be hydrodesulfurized inaccordance with the present invention. Suitable organic sulfur compoundsinclude sulfides, disulfides, mercaptans, thiophenes, benzothiophenes,dibenzothiophenes and the like and mixtures of two or more thereof.

Any suitable organic nitrogen compound may be hydrodenitrogenized inaccordance with the present invention. Suitable organic nitrogencompounds include amines, diamines, pyridines, quinolines, porphyrines,benzoquinolines and the like and mixtures of two or more thereof.

Organic sulfur compounds and/or organic nitrogen compounds contained inany suitable fluid stream may be hydrodesulfurized and/orhydrodenitrogenized in accordance with the present invention. Suitablefluid streams include light hydrocarbons such as methane, ethane,ethylene and natural gas, gases such as hydrogen and nitrogen, gaseousoxides of carbon, steam, and the inert gases such as helium and argon.

The invention is particularly directed to hydrocarbon-containing feedstreams which also contain organic sulfur compounds and/or organicnitrogen compounds. Suitable hydrocarbon-containing feeds include notonly those hydrocarbon containing feeds previously mentioned but alsopetroleum products and products from extraction and/or liquefaction ofcoal and lignite products from tar sands, products from shale oil andsimilar products. Suitable hydrocarbons include naphtha, distillates,gas oil having a boiling range from about 205° to about 538° C., toppedcrude having a boiling range in excess of about 343° C. and residuum.

The catalyst employed in the process of the present invention is ahydrogel derived catalyst comprising zinc titanate and alumina promotedwith cobalt and molybdenum. In general, the catalyst composition isprepared by first preparing zinc titanate which is then reduced to asmall size. The resulting material is mixed with a hydrosol of asuitable acidic material. A suitable base is then added to the mixtureto form a hydrogel. The resulting hydrogel is dried slowly and calcinedto form a hydrogel of zinc titanate and alumina.

The cobalt and molybdenum promoters are then added to the hydrogelderived catalyst of zinc titanate and the alumina. The cobalt andmolybdenum promoters may be added separately or in the form of cobaltmolybdate.

The zinc titanate portion of the catalyst composition may be prepared byintimately mixing suitable portions of zinc oxide and titanium dioxide,preferably in a liquid such as water, and calcining the mixture in thepresence of free oxygen at a temperaure in the range of about 650° C. toabout 1050° C., preferably in the range of about 675° C. to about 975°C., to form zinc titanate. A calcining temperature in the range of about800° C. to about 850° C. is most preferred because the surface area ofthe zinc titanate is maximized in this temperature range, thus producinga more active zinc titanate. The titanium dioxide used in preparing thezinc titanate preferably has extremely fine particle size to promoteintimate mixing of the zinc oxide and titanium dioxide. This produces arapid reaction of the zinc oxide and titanium dioxide which results in amore active zinc titanate. Preferably the titanium dioxide has anaverage particle size of less than 100 millimicrons and more preferablyless than 30 millimicrons. Flame hydrolyzed titanium dioxide hasextremely small particle size and is particularly preferred in preparingthe zinc titanate. The atomic ratio of zinc to titanium can be anysuitable ratio. The atomic ratio of zinc to titanium will generally liein the range of from about 1:1 to about 3:1 and will preferably lie inthe range of from about 1.8:1 to about 2.2:1 because the activity of thezinc titanate is greatest for atomic ratios of zinc to titanium in thisrange. The term "zinc titanate" is used regardless of the atomic ratioof zinc to titanium.

The zinc titanate portion of the catalyst composition may also beprepared by coprecipitation from aqueous solutions of a zinc compoundand a titanium compound. The aqueous solutions are mixed together andthe hydroxides are precipitated by the addition of ammonium hydroxide.The precipitate is then washed, dried and calcined, as described in thepreceding paragraph, to form zinc titanate. This method of preparationis less preferred than the mixing method because the zinc titanateprepared by the coprecipitation method is softer than the zinc titanateprepared by the mixing method.

The resulting zinc titanate is reduced to a suitable size for mixingwith a hydrosol alumina by any suitable method such as treatment in anultrasonic disrupter. The zinc titanate may be reduced to any suitablesize with a particle size in the range of about 1 to about 10 micronsbeing preferred.

The resulting zinc titanate having a fine particle size is mixed with ahydrosol of alumina. Any suitable form of alumina may be utilized.Alumina hydrate is particularly preferred because a hydrosol of aluminahydrate is readily converted to a hydrogel and then to the oxide phaseafter calcination.

After the zinc titanate has been thoroughly mixed into the hydrosol, asuitable base is added to convert the hydrosol to a hydrogel. Anysuitable base such as alkali metal hydroxides, ammonium hydroxide, orurea may be utilized. Ammonium hydroxide is the preferred base becauseit does not have any metallic component that would remain in thehydrogel.

The resulting hydrogel is dried slowly so that water will not be removedso rapidly that the hydrogel structure will collapse which would resultin excessive loss of pore volume and surface area of the finished zinctitanate hydrogel. Any suitable drying time can be utilized which doesnot result in too rapid removal of water. Preferably, the drying time isin the range of about 8 hours to about 24 hours.

Any suitable temperature can be utilized for the drying of the zinctitanate hydrogel but again the temperature should be such that toorapid a removal of water does not result. The temperature is preferablyin the range of about 35° C. to about 150° C. The most preferred dryingcondition is to start the drying process at about 80° C. and increasethe temperature slowly to about 120° C. during the drying time.

After the zinc titanate hydrogel has been dried, the zinc titanatehydrogel derived catalyst is calcined in the presence of free oxygen.Any suitable free oxygen-containing gas may be utilized with air beingpreferred because of its availability. Also, any suitable time andtemperature for the calcining may be utilized with a preferred timebeing about two hours and a preferred temperature being in the range ofabout 425° C. to about 650° C. and more preferably in the range of about480° C. to about 600° C. Although the dried zinc titanate hydrogel canbe placed directly into a preheated furnace or kiln for calcining, it ispreferable for the catalyst to attain its final temperature during aheating period of about two hours.

The hydrogel derived catalyst of zinc titanate and alumina can containany suitable weight percent of zinc titanate. In general, the amount ofzinc titanate in the hydrogel derived catalyst of zinc titanate andalumina will be in the range of from about 10 weight percent to about 50weight percent based on the total weight of the hydrogel of zinctitanate and alumina and will more preferably be in the range of fromabout 20 weight percent to about 40 weight percent based on the totalweight of the hydrogel derived catalyst of zinc titanate and alumina.

Either the elemental form of the promoters or any suitable compounds ofthe promoters may be used to form the catalyst composition.

Cobalt compounds suitable for use as a promoter are cobalt acetate,cobalt carbonate, cobalt nitrate, cobalt oxide, cobalt sulfate, cobaltthiocyanate, and the like and mixtures of two or more thereof.

Molybdenum compounds suitable for use as a promoter are ammoniummolybdate, potassium molybdate, molybdenum oxides such as molybdenum(IV) oxide and molybdenum (VI) oxide and the like and mixtures of two ormore thereof.

The promoting elements can be added to the catalyst by any method knownin the art. The cobalt, and molybdenum may be added individually byimpregnating the hydrogel with a solution-aqueous or organic-thatcontains a promoting element. After the promoting element has been addedto the hydrogel, the hydrogel is dried.

After drying to remove essentially all the solvent, a solution ofanother promoting element is added by impregnation if both the cobaltand molybdenum are not added in one step in the form of cobaltmolybdate. The sequence in which the promoting elements are added isimmaterial.

After the cobalt and molybdenum have been added, the catalystcomposition is calcined in the presence of oxygen at a temperature inthe range of about 500° to about 650° C. until volatile matter isremoved and the promoting elements are substantially converted to theiroxides. The time required for calcining step may range from about 0.1 toabout 10 hours.

Any suitable atomic ratio of cobalt to molybdenum may be utilized. Theatomic ratio of cobalt to molybdenum is generally in the range of fromabout 0.1:1 to about 3:1 and is more preferably in the range of fromabout 0.6:1 to about 0.7:1. In like manner, any suitable concentrationof cobalt and molybdenum may be utilized. The cobalt and molybdenum willbe present in the catalyst in the oxide form and the concentration ofcobalt oxide plus molybdenum oxide will generally be in the range fromabout 2 to about 25 weight percent based on the the weight of the totalcatalyst composition and will more preferably be in the range of about10 to about 20 weight percent based on the weight of the total catalystcomposition.

The process of this invention can be carried out by means of anyapparatus whereby there is achieved a contact with the catalyst of theorganic compounds to be hydrodesulfurized and/or hydrodenitrogenized.The process is in no way limited to the use of a particular apparatus.The process of this invention can be carried out using a fixed catalystbed, fluidized catalyst bed, or moving catalyst bed. Presently preferredis a fixed catalyst bed.

In order to avoid any casual and potentially hazardous mixing of thefeed stream containing the organic sulfur compound and/or organicnitrogen compound and the oxygen-containing fluid utilized in theregeneration step, provision is preferably made for terminating the flowof feed to the reactor and injecting an inert purging fluid such asnitrogen, carbon dioxide or steam. Any suitable purge time can beutilized. The purge duration will be of sufficient length to completelyremove hydrogen and hydrocarbons. Any suitable flow rate of the purgefluid may be utilized. Presently preferred is a purge fluid flow rate inthe range of from about 800 GHSV to about 1200 GHSV.

Any suitable temperature for hydrodesulfurization and/orhydrodenitrogenation of the organic sulfur compounds and/or organicnitrogen compounds over the catalyst composition of the presentinvention can be utilized. The temperature will generally be in a rangeof from about 205° C. to about 538° C. and will more preferably be inthe range of from about 316° C. to about 427° C. for thehydrodesulfurization process and/or the hydrodenitrogenation process.

Any suitable pressure for the hydrodesulfurization and/orhydrodenitrogenation of the organic sulfur compounds and/or organicnitrogen compounds over the catalyst composition of the presentinvention can be utilized. In general, the pressure will be in the rangeof from about 200 to about 3000 psig total system pressure for theprocess. The total system pressure is the sum of the partial pressure ofthe feedstock plus the partial pressure of the added hydrogen.Preferably the total system pressure will be in the range of from about400 to about 1000 psig for the hydrodesulfurization process and/or thehydrodenitrogenation process.

To maintain the activity of the catalyst, the temperature of thehydrodesulfurization and/or hydrodenitrogenation process is graduallyincreased to compensate for loss of catalyst activity due to fouling ofthe catalyst. When the temperature of the hydrodesulfurization and/orhydrodenitrogenation process cannot conveniently be increased further,the catalyst is typically regenerated by terminating the flow of feed tothe reactor and purging with an inert fluid such as nitrogen to removecombustibles and then introducing free oxygen-containing fluid tooxidize the carbonaceous deposits which have formed on the catalystduring the hydrodesulfurization and/or hydrodenitrogenation process. Thecatalyst will generally be utilized for a year or longer before beingregenerated.

The amount of oxygen, from any source, supplied during the regenerationstep will be in an amount sufficient to remove carbonaceous materialsfrom the catalyst. The regeneration step is conducted at generally thesame pressure recited for the hydrodesulfurization and/orhydrodenitrogenation step. The temperature for the regeneration step ispreferably maintained in the range of from about 425° C. to about 650°C. If the hydrodesulfurization and/or hydrodenitrogenation process hasbeen proceeding at a temperature lower than 425° C., the temperature ofthe catalyst should be increased to about 425° C. prior to the start ofthe regeneration of the catalyst in order to remove any carbonaceousdeposits on the catalyst within a reasonable time. After regeneration iscomplete the pre-sulfiding procedure is repeated for optimum catalystactivity.

The following examples are presented in further illustration of theinvention.

EXAMPLE 1 Catalyst Preparation

Catalyst 1

A control catalyst was prepared according to the procedure set forth inExample 6 of U.S. Pat. No. 4,287,050 by United Catalysts, Inc.,Louisville, Ky. Characteristics of the catalyst were as follows:

Surface Area 181 m² /g

Concentration of Components (weight percent based on weight of totalcatalyst composition)

Zn₂ Ti O₄ --6.74 wt %

CoO--5.09 wt %

MoO₃ --14.19 wt %

Catalyst 2

Zinc titanate was prepared in the same manner as the zinc titanate usedin the preparation of Catalyst 1. Then 27 grams of the thus preparedzinc titanate was slurried in 500 mL of water. The resulting slurry wasthen treated with the transducer of an ultrasonic disrupter at highpower for ten minutes to reduce the particle size of the zinc titanateto a size in the range of about 2 to about 10 microns. The resultingslurry containing the reduced particle-size zinc titanate was thencombined with a suspension of 243 grams of alpha-alumina monohydrate and900 mL of water. Sufficient nitric acid was added to the resultingmixture to lower the pH of the resulting mixture from 7.0 to 3.0 toproduce a hydrosol. Then 15 mL of concentrated ammonium hydroxide wasadded to the hydrosol to produce a hydrogel. The hydrogel was then driedin an oven for 21 hrs. at 82° C. The thus-dried hydrogel was thencalcined in air in a furnace which was heated to 649° C. during 2 hoursand then held at that temperature for 2 hours. The resulting zinctitanate hydrogel was crushed and screened.

Then 15.3 g of the resulting hydrogel was soaked in a solution of 15.3 g(NH₄)₆ Mo₇ O₂₄ 4H₂ O dissolved in 100 mL water. After excess solutionwas drained away, the impregnated hydrogel was dried under a heat lamp.The dried material was then calcined in a furnace heated to 538° C. fortwo hours.

The resulting molybdenum-impregnated zinc titanate hydrogel derivedcatalyst was then soaked in a solution of 18.5 g Co(NO₃)₂.6H₂ Odissolved in 100 mL of water. After excess solution was drained away andthe impregnated hydrogel was dried under a heat lamp. The dried materialwas then calcined at 538° C. for two hours. Characteristics of thecatalyst were as follows:

Surface Area 221 m² /g

Concentration of Components (weight percent based on weight of totalcatalyst composition)

Zn₂ Ti O₄ --8.90 wt %

CoO--3.24 wt %

MoO₃ --12.50 wt %

Catalyst 3

Following the same general procedure as for Catalyst 2, anotherpreparation was made to be even closer to Catalyst 1 in Co/Mocomposition for comparative purposes. Characteristics of the catalystwere as follows:

Surface area 216 m² /g

Concentration of Components (weight percent based on weight of totalcatalyst composition)

Zn₂ TiO₄ --9.55 wt %

CoO--4.91 wt %

MoO₃ --15.7 wt %

EXAMPLE II

Catalysts 1, 2, and 3 were used to hydrodesulfurize andhydrodenitrogenate a light cycle oil (boiling range 350°-690° F.) thatcontained 2.25 wt % organic sulfur (from added dibenzothiophene) and 166ppm (by weight) organic nitrogen. The API gravity of the oil was 23.1.

Runs were made in an automated test unit capable of testing sixcatalysts simultaneously. Six reactors 1" o.d.×0.813" i.d.×4.5" inlength and made of 316 stainless steel were disposed symmetrically in asingle furnace. The reactors operated with a fixed catalyst bed indown-flow mode. Feedstock preheat lines ran upflow through the furnace,entering the tops of the reactors where the feedstock was mixed withadded hydrogen. Conditions in the reactors were mixed phase, i.e.trickle bed process. Runs were made with 5 cc of catalyst plus 20 cc ofinert diluent (alundum). Contact time of feedstock with catalyst, interms of volume of feedstock per volume of catalyst per hour (LHSV), was5 LHSV.

All runs were made at 5.0 LHSV, 500 psig, with 5000 SCF hydrogen/bblfeed. All catalysts were presulfided first at 204° C. until hydrogensulfide was detected in the effluent flowing from the reactor, then at372° C. until hydrogen sulfide was detected in the effluent flowing fromthe reactor. Results of the runs are set forth in Table I.

                  TABLE I                                                         ______________________________________                                                 Catalyst:                                                            Temp, °F.                                                                         1             2      3                                             ______________________________________                                        Wt % Sulfur in Product                                                        525        --            --     .93                                           550        .98           .94    .75                                           600        .51           .45    .19                                           650        .099          .070    0.24                                         700        .026          .020    .010                                         750        .013          .017    .0072                                        (Sulfur in Feed = 2.25 wt %)                                                  PPM Nitrogen in Product                                                       525        --            --     52                                            550        57            51     41                                            600        50            45     38                                            650        40            32     16                                            700        33            25     15                                            750        24            21     13                                            (Nitrogen in Feed = PPM)                                                      ______________________________________                                    

The results shown in Table I indicate significantly more sulfur andnitrogen are removed from the feed by Catalysts 2 and 3, the inventivecatalysts.

While the wt % S in product of catalyst 2 is 0.004 higher than thecontrol catalyst at 750° F., the overall performance of both inventivecatalysts is superior to Catalyst 1.

EXAMPLE 3

It is believed that the increase in surface area of Catalyst 2 and 3with respect to Catalyst 1 (40 m² /g in the case of catalyst 2 and 35 m²/g in the case of catalyst 3) is at least partially responsible for theimproved performance of the hydrogel derived catalyst of zinc titanateand alumina promoted with cobalt and molybdenum. One factor whichaffects the surface area is the size of the zinc titanate used in thepreparations of Catalyst 2 and 3 as opposed to the preparation inCatalyst 1. The size of the zinc titanate used in the preparation ofCatalyst 1 was about 75 microns (200 mesh) as opposed to the size in therange of about 2 to about 10 microns for the zinc titanate of Catalyst 2and 3. However, calculations based on standard equations for particlesize show that the size reduction of the zinc titanate should result inan increase in surface area of about 0.5 m² /g which is far smaller thanthe increased surface area of between 35 and 40 m² /g which was actuallydemonstrated.

Reasonable variations and modifications are possible within the scope ofthe disclosure and the appended claims to the invention.

That which is claimed is:
 1. A hydrogel derived catalyst composition comprising zinc titanate and alumina promoted with cobalt and molybdenum.
 2. A composition in accordance with claim 1 wherein said hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum is prepared by calcining a mixture of zinc oxide and titanium dioxide in the presence of free oxygen at a temperature in the range of about 650° C. to about 1050° C. to form zinc titanate, mixing the thus formed zinc titanate in a powdered form with a hydrosol of alumina hydrate to form a zinc titanate/alumina hydrosol, adding ammonium hydroxide to convert said hydrosol to a hydrogel, drying and calcining said hydrogel to form a hydrogel derived catalyst comprising zinc titanate and alumina, adding a solution or solutions of cobalt and molybdenum compounds to said hydrogel derived catalyst comprising zinc titanate and alumina and calcining said hydrogel derived catalyst comprising zinc titanate and alumina to which cobalt and molybdenum have been added, wherein said cobalt and molybdenum are present in said catalyst composition in the oxide form after the final calcining step.
 3. A process in accordance wth claim 2 wherein the concentration of zinc titanate in said hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum is in the range of about 10 to about 50 wt % based on the weight of only the hydrogel derived catalyst comprising zinc titanate and alumina and wherein the concentration of cobalt and molybdenum in said hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum is in the range of about 2 to about 25 wt % based on the weight of the hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum.
 4. A process in accordance with claim 2 wherein the concentration of zinc titanate in said hydrogel derived catalyst comprising zinc titanate and alumina promited with cobalt and molybdenum is in the range of about 20 to about 40 wt % based on the weight of only the hydrogel derived catalyst comprising zinc titanate and alumina and wherein the concentration of cobalt and molybdenum in said hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum is in the range of about 10 to about 20 wt % based on the weight of the hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum.
 5. A process in accordance with claim 2 wherein the atomic ratio of zinc to titanium in said hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum is in the range of about 1:1 to about 3:1 and wherein the atomic range ratio of cobalt to molybdenum in said hydrogel of zinc titanate and alumina promoted with cobalt and molybdenum is in the range of about 0.1:1 to about 3:1.
 6. A process in accordance with claim 2 wherein the atomic ratio of zinc to titanium in said hydrogel derived catalyst comprising zinc titanate and alumina promoted with cobalt and molybdenum is in the range of about 1.8:1 to about 2.2:1 and wherein the atomic range ratio of cobalt to molybdenum in said hydrogel of zinc titanate and alumina promoted with cobalt and molybdenum is in the range of about 0.6:1 to about 0.7:1.
 7. A process in accordance with claim 2 wherein said hydrogel derived catalyst comprising zinc titanate and alumina is dried for a time in the range of about 8 to about 24 hours and at a temperature in the range of about 35° C. to about 150° C.
 8. A process in accordance with claim 7 wherein the dried hydrogel derived catalyst comprising zinc titanate and alumina is calcined in the presence of free oxygen at a temperature in the range of about 425° C. to about 650° C. for a time of about 2 hours.
 9. A process in accordance with claim 7 wherein said hydrogel derived catalyst comprising zinc titanate and alumina to which cobalt and molybdenum have been added is calcined in the presence of free oxygen at a temperature in the range of about 500° C. to about 650° C. for a time in the range of about 0.1 to about 10 hours. 